Mouldings for automobiles are installed chiefly for a decorative purpose for example on automotive doors. Such mouldings also serve a protective purpose by preventing damage to door and side panels of a vehicle caused by minor impacts. Recent mouldings are in most cases manufactured by a gas injection moulding process. The gas injection moulding process is a process for manufacturing a plastics moulding by providing a thick-wall portion called a gas channel in the moulding, incompletely filling a molten resin in this thick-wall portion, and then blowing a gas into the gas channel during or after filling the molten resin.
The gas channel is mostly provided in a central portion in the direction of width. According to the gas injection moulding process, the molten resin is moved by a gas pressure in the direction of width of the gas channel. Therefore, the travel of the molten resin must be uniform in the direction of width, or there will occur such defects as weld, ununiform resin dispersion, sinking, and others, resulting in an desirable non-uniform hollow portion having decreased strength.
There are also used mouldings each having two or more gas channels. For example, some mouldings are provided with gas channels in both side edges in the direction of width, so that a molten resin goes from the side edges to the central part in the direction of width. For even such a moulding, it is designed that the molten resin moves for an equal travel as in the case of the moulding having the gas channel in the central part in the direction of width.
In prior art mouldings, the gas injection aperture for filling the gas in the gas channel is provided on the extension of the gas channel. However, the adoption of such a structure is accompanied by the following problem.
In the case of a moulding attached on an automotive body, water such as rain water is likely to enter the hollow portion through the gas injection aperture made in the moulding. The water that has once entered will stay in the hollow portion, and will leak out little by little during travel of the automobile, staining the automobile.
Closing the gas injection aperture can prevent the entrance of rain water, etc., but this is impractical because it will increase manufacturing process and cost.
Japanese Utility Model Laid-Open No. 63255/1990 gives an example of a prior art moulding for automobiles, in which a gas injection aperture 3 is provided in the back side 4 of the moulding corresponding to a hollow portion 2. The water that has entered at the gas injection aperture 3 stays in the lower edge of the hollow portion 2 and cannot be discharged.
It is an object of the present invention to provide an automotive moulding designed to prevent entrance of rain water, etc. into a hollow portion.